1. Field of the Invention
The present invention relates generally to wireless and wired communication systems, and in particular relates to radio-over-fiber (RoF) communication systems that employ wired and/or wireless technology.
2. Technical Background
Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, so-called “wireless fidelity” or “WiFi” systems and wireless local area networks (WLANs) are being deployed in many different types of areas (coffee shops, airports, libraries, etc.). Wireless communication systems communicate with wireless devices called “clients,” which must reside within the wireless range or “cell coverage area” in order to communicate with the access point device.
One approach to deploying a wireless communication system involves the use of “cells,” which are radio-frequency (RF) coverage areas. Cells can have relatively large radii (e.g., 1000 m) or can have relatively small radii (“picocells”) in the range from about a few meters up to about 20 meters. Because a picocell covers a small area, there are typically only a few users (clients) per picocell. Picocells also allow for selective wireless coverage in small regions that otherwise would have poor signal strength when covered by larger cells created by conventional base stations.
The essential components that make up a RoF wireless cellular system are a head-end controller (“head end”), one or more optical fiber cables, and one or more transponders. The optical fiber cables are connected at one end to the head-end controller. The transponders are optically coupled to the optical fiber cables along the length of the cables. The optical fiber cables have downlink and uplink optical fibers that carry RoF optical signals between the transponders and the head end. The transponders convert RoF optical signals to electrical signals and vice versa to create the corresponding one or more cells. The transponders include one or more antennas that transmit and receive RF free-space electromagnetic (EM) signals to and from the client devices within the corresponding cell. Combining a number of transponders creates an array of cells that cover an area called a “cellular coverage area.” A closely packed array of picocells forms a picocellular coverage area that provides high per-user data-throughput.
While RoF wireless cellular and picocellular systems are robust, it is desirable to be able to provide state-of-the-art wireless and wired services to end-users—for instance, in present day technology terms, a wireless RoF infrastructure with IEEE 802.11a/b/g/n along with Gigabit Wireline Ethernet, and a wired infrastructure with IEEE 802.3/u./z (where IEEE 802.3 is 10 Mbps, IEEE 802.3u is 100 Mbps and IEEE 802.3z is 1 Gbps). The traditional way of achieving this is through two separate wireless and wired network infrastructures, which is costly and complicated to deploy and maintain.
What is needed is an approach that allows for both wireless and wired services to be provided to end-users without the complexity and cost of having to deploy two separate communication systems.